The present invention relates to an eyeglass lens processing apparatus for processing a peripheral edge of an eyeglass lens.
In a eyeglass lens processing apparatus for processing a peripheral edge of an eyeglass lens by a plurality of grindstones such as a roughing grindstone for a glass lens, a roughing grindstone for a plastic lens and a finishing grindstone for beveling and flat-processing are attached to a grindstone rotating shaft side by side in a parallel relation with lens chuck shafts, and the plurality of grindstones are integrally rotated (for example, see U.S. Pat. No. 6,095,896 (JP-A-11-70451)). Further, there is a structure in which a polishing grindstone is coaxially attached thereto. The peripheral edge of the eyeglass lens held by the lens chuck shafts is first processed by the roughing grindstone. At this time, an axis-to-axis distance between an axis of the lens chuck shafts and an axis of the grindstone rotating shaft varies based on target lens shape data to rough the peripheral edge of the lens while a predetermined finish margin remains.
In recent years, the design of an eyeglass frame has been diversified and many eyeglass frames having a steep frame curve have been proposed. In this case, the eyeglass lens also has a steep lens curve according to the frame curve (“high curve lens”).
However, as in the above-described apparatus, when the high curve lens having the steep lens curve is to be roughed by only controlling the axis-to-axis distance between the lens chuck shafts and the grindstone rotating shaft, there is a possibility that the lens protrudes (deviates) from a width of the roughing grindstone. If the periphery edge of the lens is roughed while the lens protrudes from the width of the roughing grindstone, the periphery edge of the lens may be brought into contact with the finishing grindstone provided next to the roughing grindstone, or the processing moves to the finishing processing in a state that a part which should be roughed remains. In this case, there is a feat that an excess load, an axial deviation, or deformation and crack of the lens occurs at the time of the processing. If the width of the roughing grindstone is made sufficiently wide, a size of the apparatus becomes large.